Induction of Labor: Indications and Methods
When Induction of Labor is Recommended
Induction of labor should be performed when medical or obstetric conditions make continuing pregnancy riskier than delivery, with specific evidence-based timing for common indications. 1
Medical and Obstetric Indications
- Gestational hypertension or mild preeclampsia at ≥37 weeks' gestation should prompt induction to improve maternal outcomes 1
- Post-term pregnancy at ≥41 weeks warrants induction 1
- Premature rupture of membranes at term requires induction immediately or within 12 hours if labor has not begun 2
- Maternal diabetes with poor glycemic control is an indication for induction 1
- Rh disease requiring delivery 1
Elective Induction at 39 Weeks
For low-risk nulliparous women, elective induction at 39 weeks 0 days is recommended to reduce cesarean delivery and hypertensive complications. 1 This represents a paradigm shift in obstetric practice:
- Cesarean delivery rate decreases from 22.2% to 18.6% (RR 0.84, NNT=28) 1
- Hypertensive disorders reduce from 14.1% to 9.1% (RR 0.64) 1
- No increase in adverse neonatal outcomes occurs 1
Critical Contraindications
Elective induction must not be performed before 39 weeks 0 days due to increased neonatal respiratory morbidity. 1, 3
- Prior classical (vertical) or T-shaped uterine incision is an absolute contraindication due to uterine rupture risk 3
- Suspected fetal macrosomia alone is NOT an indication for induction and doubles cesarean risk without reducing shoulder dystocia 1, 3
- Unstable maternal medical conditions contraindicate induction 3
Methods of Labor Induction
Cervical Ripening for Unfavorable Cervix
For women with an unfavorable cervix, combined mechanical and pharmacologic methods are most effective. 2
Mechanical Methods
- 60-80 mL single-balloon Foley catheter for 12 hours should be used as first-line cervical ripening 2
- Mechanical methods (Foley catheter) have lower uterine rupture risk in women with previous cesarean compared to pharmacologic agents 3
- In patients with cardiac disease or cyanosis, mechanical methods are preferred to avoid systemic vascular resistance drops 1
Pharmacologic Methods - Misoprostol
Oral misoprostol 25 μg every 2-4 hours is the preferred pharmacologic agent for cervical ripening. 2
- Oral route is superior to vaginal, with less uterine hyperstimulation (RR 0.69) 4
- Oral administration results in fewer cesarean deliveries compared to vaginal dinoprostone (RR 0.84) 4
- ABSOLUTE CONTRAINDICATION: Misoprostol must never be used in women with prior cesarean delivery due to 13% uterine rupture risk 1, 3, 4
- Avoid in advanced liver failure due to hepatic metabolism requirements 1, 4
Pharmacologic Methods - Dinoprostone
- Avoid in active cardiovascular disease due to profound blood pressure effects 1
Labor Induction with Favorable Cervix
Combined amniotomy and intravenous oxytocin is the most effective approach for women with a favorable cervix. 5
Oxytocin Administration Protocol
- Initial dose: 1-2 mU/min intravenously 6
- Gradually increase by 1-2 mU/min increments until normal labor contraction pattern established 6
- Requires continuous infusion pump and frequent monitoring of contractions and fetal heart rate 6
- Once 5-6 cm cervical dilation achieved, consider discontinuing oxytocin if adequate contractions present 2
Timing of Cesarean Decision
Cesarean delivery should not be performed before 15 hours of oxytocin infusion with amniotomy, and ideally wait 18-24 hours. 2 This prevents premature diagnosis of failed induction.
Special Considerations for Anticoagulation
Women receiving prophylactic LMWH should be allowed spontaneous labor rather than scheduled induction when possible. 7 However, for therapeutic-dose anticoagulation, individualized multidisciplinary planning is required regarding delivery timing and neuraxial anesthesia access 7